How to play only bass or discant staff- and yes, yes, I readed all what found from internet

Just normal piano note. Or, in my case accordion.

How I can play ONLY one staff? So, eg. playback only bass.

Yes. Answer is: "Delete temporary staff you dont want listen". This is only answer.

1. No. "Instruments" there is only "accordion" and "bass", "discant" (sorry... finnish version...). I can HIDE staff I want, but this make no effect in playback.
2. Using timebar I can select bass or discant, BUT in this timebar no any too make "mute".
3. Mixer. I can see only "Accordion", "ms basic/metronom", Aux1, aux2, master. But. In mixer it is possible adjust volume- common, master volume, but no adjust for one staff.

Of course I found all information how to use mixer, but how I can use mixer if there is no separate bass/discant? Or, instruments- same problem.

I am sure this must be any basic function start from musescore 1, but... "how to activate"...